Apparatus for taping closed coils

ABSTRACT

APPARATUS FOR WRAPPING AN INSULATING TAPE ON A RECTANGULARLY SHAPED, PREWOUND PRIMARY COIL OF A LIGHTING TRANSFORMER. AN ENDLESS BELT PASSES ABOUT A PLURALITY OF GUIDE ROLLERS ONE OF WHICH IS MOVABLE LATERALLY FOR RELEASE OF THE BELT TENSION. THE GUIDE MEANS INCLUDES A PAIR OF DRIVE WHEELS FRICTIONALLY ENGAGING THE INNER PERIPHERY OF BELT AND PROVIDING MOVEMENT THEREOF. THE DRIVE WHEELS ARE MOUNTED IN SPACED RELATION SLIGHTLY GREATER THAN THE MAXIMUM WIDTH OF TAPE AND THE BELT IS PULLED INWARDLY BETWEEN THE TWO DRIVE WHEELS TO DEFINE AN INNER DRIVE LOOP. THE COIL IS DISPOSED WITHIN THE LOOP AND BY INCREASING THE BELT TENSION IS MOVED OUTWARDLY INTO FRICTION DRIVING ENGAGEMENT WITH THE BELT AT THE POINT OF CONTACT TO THE DRIVE WHEELS. A WRAPPING HEAD IS DRIVEN IN TIMED RELATION WITH THE DRIVEN COIL TO APPLY OVERLAPPING TURNS OF TAPE ON THE COIL.

' Sept 20; 1-971 v J. JR. BURTON I APPARATUS FOR TAPING CLOSED COILS Filed Sept. '12, 1968 3 Sheets-Sheet 1 INVENTOR. James R. Burton ll/lornc 3 I In.

I J. R. fBuR'roN Y APPARATUS Fdii TAPING CLOSED COILS} Sept. 29,1971

3 Sheets-Sheet:

Filed Sept. 12, 1968 mvsmoa James R. Burton BY ll III I ls l l hhdllnl Sept. 20, 1971 I J. R. BURTON APPARATU TAPING CLOSED COILS 5.Sheets-Sheet 5 Filed se t'. 12, 1968 IN VENTOR.

L M a J 7 United States Patent 01 ice U.S. c1. 242-6 3 Claims ABSTRACT OF THE DISCLOSURE Apparatus for wrapping an insulating tape on a rectangularly shaped, prewound primary coil of a lighting transformer. An endless belt passes about a plurality of guide rollers one of which is movable laterally for release of the belt tension. The guide means includes a pair of drive wheels frictionally engaging the inner periphery of belt and providing movement thereof. The drive wheels are mounted in spaced relation slightly greater than the maximum width of tape and the belt is pulled inwardly between the two drive wheels to define an inner drive loop. The coil is disposed within the loop and by increasing the belt tension is moved outwardly into friction driving engagement with the belt at the point of contact to the drive wheels. A wrapping head is driven in timed relation with the driven coil to apply overlapping turns of tape on the coil.

This invention relates to an apparatus for applying a strip-like tape element to a closed endless member and particularly to such apparatus and method for applying an indefinite length of insulating tape to a high voltage transformer coil assembled as an integrated component of a lighting fixture or the like.

Transformers and other electrical inductive devices may employ prewound coils suitably insulated and then assembled with magnetic cores. For example, in the development of exterior lighting devices for streets and large areas, mercury and fluorescent devices have been developed to provide more efficient lighting. Mercury lighting units and the like preferably include individual insulation to prevent breakdown under operating conditions.

A high voltage coil wound or disposed in close coupled relation to a core must have the insulation uniformly applied to prevent areas or points of high electrical stress between the coil and the core in order to prevent the electrical phenomena of corona. The insulation replaces the air between the coil and the core which in turn tends to increase the electrical stress in the air. As is well known, free electrons in the air space remaining can be accelerated sufficiently to cause a cascade of secondary electrons if the stress is sufficiently high. This is known as the corona discharge effect and can, over a long period of time, adversely affect the insulating characteristics of the insulation with actual destruction thereof under certain circumstances. The construction must therefore provide sufiicient air space such that cnder operating conditions, all corona originating above the maximum operating voltage level is extinguished at some point above the rated operating voltage as the voltage is reduced.

For example, the primary coils of constant current transformers which are employed in the lighting industry 3,606,190 Patented Sept. 20, 1971 must be insulated sufliciently to pass a withstand test applying alternating 6O cycle power of 19,000 volts to the primary coil for one mniute. Further, when they are integrated into and form a part of the lighting fixture, the combination must pass a similar withstand test without flashover. The latter requirement makes it essential that the string distance between all bare connections of the primary and the grounded lamp be sufficiently large to prevent possible flashover. For example, in one practical construction, 1% inches constituted a minimum length to pass industry standards.

Because of the severe requirements imposed by the above practical considerations, the industry has generally formed prewound coils and wrapped them by hand methods with a suitable tape, for example, a mica polyester. The tape is measured to the necessary length in accordance with the coil size, wound on a suitable hand shuttle and then transferred to the coil by a manual operation with half lapping of the adjacent convolutions of the tape, that is, covering one-half of the preceding turn with the immediately following turn. The half lap has been found to establish a necessary creepage distance while minimizing excessive tape build-up with a resulting adverse corona effect. If the turn should be lapped less than a half, the creepage distance is reduced. If the lap is gretaer, the buildup of tape may become excessive with the resulting corona effect. The manual application, however, is repetitious and requires extremely close attention. As a result, it is an exceptionally fatiguing process with the usual disadvantages in quality control. The rejection rate is also relatively substantial with a corresponding increase in the cost and time factors.

The present invention is particularly directed to an automatic or semi-automatic apparatus and method of applying tape to an endless member, such as the prewound coils of a transformer, in a manner resulting in the pre cision application of the tape with the selected lapping of successive turns such that the desired electrical creep age and basic insulation is provided in a manner establishing and maintaining an optimum and long life coil unit.

Generally, in accordance with the present invention, the coil is mounted in a wrapping machine having a means engaging the outer peripheral surface of the coil and clamping the coil into engagement with a frictional rotating drive means to cause the timed rotation of the coil. A tape winding means is mounted to continuously wrap a selected size tape about the coil as it is rotated about the shuttle. In order to provide a desired close wrapping, substantial friction forces must be established between the outside surface of the coil and the friction drive means. This is particularly true with respect to a coil formed in a generally rectangular manner having corners of a relatively small radius.

Applicant has found that unusually satisfactory and highly reliable movement of the coil is obtained by a belt drive which provides maximum frictional area with the coil unit. This particularly novel apparatus and method includes a belt mounted to be clamped about the exterior of at least a portion of the coil with means to move the belt while maintaining heavy frictional engagement with a substantial portion of the exterior surface of the coil. In a preferred construction, an endless belt is mounted to pass about a plurality of suitable guide means at least one of which is movable laterally of the belt to allow release of the tension of the belt. The guide means include drive rollers frictionally engaging the inner periphcry of the belt and providing movement thereof. The coil is disposed with the belt looped about the coil and in particular, with the surface of the belt frictionally engaging the surface of the coil and pulling it into engagement with a suitable rotatable means. In a preferred construction, the latter means included a pair of drive wheels or rolls mounted in spaced relation slightly greater than the maximum width of the tape. The belt is pulled inwardly between the two drive rolls to define an inner loop which passes about the drive rolls. The coil is disposed within the loop. When the tension means is drawn up, the belt is pulled outwardly onto the periphery of the coil and the coil tends to move outwardly between the rolls and moves into clamping or friction driving engagement with the belt as the point of contact to the drive rolls.

The present invention has provided relatively rapid, reliable and repeatable wrapping of a series of coils in a production line process. The fixture and apparatus can readily handle a relatively wide range of different size coils, as well as any shape from round to rectangular.

The drawings furnished herewith illustrate the best mode presently contemplated by the inventor of carrying out the invention and disclose the above advantages and features, as well as others which will be readily understood from the following description of the drawings.

In the drawings:

FIG. 1 is a side elevational view of an exterior lighting unit incorporating a transformer constructed in accordance with the present invention;

FIG. 2 is an enlarged view of the transformer shown in FIG. 1;

FIG. 3 is an elevational view of a coil shown in FIGS. 1 and 2 prior to wrapping with insulation;

FIG. 4 is a pictorial view illustrating the coil disposed in a tape-applying apparatus constructed in accordance with the present invention;

FIG. 5 is a top elevational view of the fixture shown in FIG. 4;

FIG. 6 is a fragmentary side elevational view of the fixture shown in FIGS. 4 and 5; and

FIG. 7 is a fragmentary view generally taken on line 7-7 of FIG. 6.

Referring to the drawings and particularly to FIG. 1, the present invention is shown applied to a street lighting fixture 1 of a mercury vapor variety and includes a component housing 2 mounted on a pole 3. A lamp socket 4 is supported within the housing 2 and projects upwardly into a tubular refractor 5. The lamp socket 4 is electrically connected to the secondary coil of winding 6 of a transformer 7. Incoming power lines 8 project upwardly through the pole 3 and are connected to the primary coil of winding 9 of the transformer 7 to establish proper energization of the lamp 10. The transformer 7 includes a generally rectangular three-legged core 11 with the primary and secondary windings 6 and 9 disposed in stacked relation on the central leg 12.

The core is secured within the housing 2 by a suitable bracket 13. The present invention is particularly directed to a method and apparatus of constructing the primary winding or the like which is more clearly shown in FIGS. 2 and 3 and is more fully described as follows.

The coil or winding 9 is formed of a suitable insulated wire and wound into a generally rectangular configuration defining relatively long and straight side portions interconnected by curved end portions. The coil 9 terminates in a pair of leads 14 adjacent the one end and is wrapped with a multiple layer insulation which is formed from overlapping of a continuous length of an insulating tape or strip 15. The coil is wound with the straight side portions to provide optimum spacing with respect to the laminated core, which for reasons of most economical construction, includes similar sized interleaved laminations defining the straight central leg upon which the coils are mounted.

Insulating spacers 16 are disposed between the coils 6 and 9 and similar spacers 17 are located between the opposite end of coil 9 and adjacent core 11. Further, strip 4 insulating spacers 18 are located between the inner sides of the coil 9 and the sides of the central leg 12 of the core 11.

In the construction and assembly of the coil 9 with the core 11, the thickness and distribution of the insulation 15 on the coil 9 and the spacing of the coil 9 from the surfaces of the core 11 and from the secondary coil 6, must be established to prevent possible fiashover and/or corona discharge. The minimum spacing requires that the coil sides be parallel to the sides of the core 11. As the laminations are the same and thus define straight legged portions, the coil sides which pass through the openings must also be straight. Further, the insulation 15 must be evenly distributed to prevent high electrical stress areas which could create a corona discharge.

The problem is particularly significant in the transformer structure of a lighting fixture, such as shown in the drawings, because of the small size requirement placed on the transformer unit. The total assembly, in order to meet industry standards, must have the insulation 15 properly applied to prevent corona effect and must have all bared connections of the primary coil 9 spaced in excess of 1% inches from the grounded lighting housing 2 in order to prevent flashover underrequired tests.

The coil 9, as shown in FIG. 3, is wound of suitable multiple numbers of turns of a conductor with the leads 14 projecting laterally along the centerline of the coil on the exterior of one narrow coil side. The leads 14 are suitably insulated with a shrunk insulating tubing 19 or the like with the outer ends bared for connection to the primary connector 20, as shown in FIG. 1. The leads 14 and individual turns are secured in place by suitable thin strips of insulating tape 21 adjacent the leads and centrally of the other three sides to support the turns for receiving the overlapped insulating strip or tape 15.

The present invention is particularly directed to an automatic apparatus and method for applying the insulation 15 and a preferred construction is shown in FIGS. 4-6, inclusive.

Referring particularly to FIGS. 46, the illustrated construction of the wrapping machine 22 include a working support or fixture 23 on which the unwrapped coil 9 is mounted with respect to a shuttle-type wrapping head 24. An indefinite length of insulation tape 25 is fed through the head 24 and mechanically wound upon the aligned portion of the coil 9.

The basic wrapping head 24 may be of any suitable construction adapted to take a tape strip and wrap it around a member aligned with the head. The illustrated embodiment of the machine is a commercially available device and identified by model #TO127 produced by Leesona Corporation of Danbury, Conn. and generally shown in United States Pat. No. 2,793,817. The present invention is directed to the fixture structure and particularly the means for supporting and moving of the coil with respect to bobbin or shuttle head 24 and consequently only this portion is described in detail.

In accordance with the illustrated embodiment of the present invention, a rotating endless belt 26 is mounted to form a part of the fixture 23 and frictionally engages a substantial portion of the outer periphery of the coil 9. The belt 26 is slowly rotated and correspondingly rotates the coil 9 past the shuttle head 24 to provide for a con tinuous multiple layer wrap of tape 25 upon the coil with each turn being applied in accurate overlapping relation to the immediately preceding turn; for example, precisely one-half of the width of the tape. The particular overlap is controlled by regulating the relative speed of rotation of the coil 9 and the wrapping of tape 25 by the head 24.

More particularly, the fixture 23 includes a base or support plate 27 interconnected by an adjustable mount 28 to a table or bed 29 of the wrapping machine 22. The illustrated mount 28 is adjustably clampedwithin a slot 30 to allow movement toward and away from the shuttle head 24. The plate 27 is correspondingly located in accordance with the particular coil size.

A pair of drive rolls or wheels 31 and 32 for belt 26 are similarly secured to the outer end of mounting arms 33. The inner end of each arm 33 is releasably secured to the mount 28 by a pivot connection 34, and the outer end terminates immediately outwardly of the plate 27 adjacent head 24. The wheels 31 and 32 are spaced slightly greater than the width of the wrapping tape 25. Generally, the wheels 31 and 32 are located as close together as possible without interfering with tape 25 to firmly hold the coil 9 and prevent any uncontrolled movement of the coil 9. The drive wheel 31 is carried on a shaft 35 which is rotatably mounted in the outer end of the arm 33 and locates the wheel generally just above the top plane of the plate 27.

As most clearly shown in FIGS. and 6, a positive drive belt 36 is coupled to the corresponding shaft 37 which is secured to the underside of the plate 27. The axis of member 37 and the pivotal connection of arm 33 are coincident to permit adjustment of the angular position of arm 33.

A gear 38 is connected to the member 37 and meshes with a large driven gear 39 which is rotatably mounted between the two arms 33. The gear 38 is reversibly driven to correspondingly drive the wheel 31 through the gear and belt drive train.

The wheel 32 is similarly mounted and driven to the opposite side of head 24, and correspondingly elements are identified by corresponding primed numbers.

The large gear 39 is secured to the upper end of a shaft 40 which is journaled in the adjustable mount 28. The

shaft 40 extends into the bed 29 of machine 22 and terminates in a worm gear 41. An elongated worm 42 is r0- tatably mounted in depending brackets 43 on the underside of table 29 and in mesh with the gear 41 and driven through a bevel gear unit 44. The elongated worm 42 maintains engagement of the worm gear 41 for all posi tions of the mount 28 with respect to the head 24. As most clearly shown in FIG. 7, a bevel gear 45 of unit 44 is secured to the one end of worm shaft 46 and selectively engages a pair of opposite disposed bevel gears 47 and 48 carried by a driven shaft 49. The bevel gears 47 and 48 are secured to a sleeve 50 which is vslidably mounted and keyed on the shaft 49 and selectively positioned to The particular system for head 24 may be of any suitable known or desired construction and no further description thereof is given. The head drive system preferably includes means for adjusting the wrapping speed in accordance with the usual commercial practice.

The head 24 and belt 26 are thereby simultaneously driven in fixed timed relationship. The relative speed of the belt 26 and head 24, determine the particular overlap of the tape and for the particular application under consideration is selected to establish a one-half lap.

Each wheel 31 and 32 is shown formed of a relatively hard rubber and of a depth slightly in excess of the depth of the belt 26. The belt 26 is shown as an endless memher which may be formed of rubber or other suitable material. The belt 26 is stretched about the drive wheels 31 and 32 and a pair of guide spools 53 and 54 disposed to the opposite sides of the plate 27, slightly outwardly of the drive wheels 31 and 32, and a tension roller or spool 55 disposed to the opposite end of the plate 27 from the drive wheels 31 and 32. The guide spools 53 and 54 are rotatably mounted in brackets 56 which are attached to the bottom side of the plate 27 and extend laterally outwardly from the side edges. The tension spool 55 is secured adjacent the outer edge cerl'trally of the drive system in the outer bifurcated end of a tension arm 57 forming a part of a latch assembly 58 to allow tightening and loosening of the drive belt 26 as most clearly shown in FIGS. 4 and 5.

A belt retainer idle roller 49 is mounted On the outer end of arm 60 which is pivotally attached to the underside of table 27. A coil spring 61 is secured to the table 27 and the arm 60 and resiliently urges the roller 59 toward the wheel 31 to clamp the belt 26 to the wheel. The spring 61 establishes a light pressure suflicient to support the belt 26 when loose but insufficient to interfere with its movement when tightened by the positioning of tension arm 57. I

The tension arm 57 is pivotally interconnected to a member 62 which in turn is pivotally secured to the plate 27 A latch arm 63 is pivotally attached to member 62 for vertical pivoting movement with respect to an armate rack 64 secured to plate 27 The underside of the latch arm 63 is provided with locking teeth adapted to mate with rack 64 and to selectively lock the arm 63 and therefore tension arm 57 in any one of a plurality of positions.

In the assembly, the arm 57 is released and the loose belt 26 is located to receive the coil 9 in an unwrapped state. In particular, the belt 26 is pulled inwardly between the drive wheels 31 and 32 to define an inner loop which is sufficiently large to allow ready insertion of the coil 9 which rests on the plate 27. The tension arm 57 is pivoted to a selected latch postion to tighten the belt 26 and establish a selected frictional engagement between the drive wheels 31 and 32 and the inner peripheral surface of the belt 26 and simultaneously to establish a frictional engagement between the outer periphery of the coil 9 and the engaging outer periphery of the belt 26. In this manner, the belt firmly exerts a hold on the coil unit tending to pull it outwardly past the head 24 and between the drive wheels 31 and 32 which act as a stop whereby the belt frictionally grasps the outer periphery of the coil 9.

Applicant has found that the illustrated belt drive provides a suflicient frictional area engagement and drive force between the drive wheels and the belt and between the coil and the belt to create a constant accurate movement of the coil through the head 24. Consequently, the shuttle head 24 may provide accurate overlapped wrapping in accordance with any desired degree of overlap.

The operator applies an initial end of the tape to the properly placed coil 9 and starts the machine 22 which drives the drive gear and pulley system for rotating the wheels 31 and 32 and simultaneously wraps the tape 25 upon the coil 9. The speed of the application of the continuous tape strip 25 and the speed of wheels 31 and 32 may be correlated to produce essentially a direct one-half overlap, or any other desired overlap, as required. The one-half overlap in the curved end portion is only attained on the outer surface of the coil 9 because of the dilference between the inner and the outer circumferences. However, the inside and the outside of the coil 9 both have a halflap on the straight sides of the coil. As this is a critical area within which the core leg 12 mates with the coil 9, the differential lap at the ends with the increased insulating thickness is not of any particular practical significance.

The radii of the corners of the rectangular coils are generally limited by the size and shape of the shuttle assembly and the width of the tape being applied. Generally, applicant has found that the minimum internal radius of the coil should be at least 75% of the width of the tape.

The machine 22 may continue to wrap the coil 9 with as many layers of insulating tape 25 as desired. In commercial practice, applicant has found that adjacent layers opposite directional drive and the same series of coils 9 are then wrapped with a second layer of insulation. The reverse drive of the belt 26 directly reverses the angular orientation of the strips 25. The desired number of layers is therefore applied by alternating the belt drive. The operator need otherwise only make sure that the leads 14 are maintained from the path of the shuttle head 24 during the wrapping operation by proper positioning thereof as that portion of the coil 9 moves through the shuttle head.

The illustrated fixture with the means to adjust the placement of the belt readily accommodates a wide range of coil sizes and shapes and is therefore particularly adapted to commercial production of the coils. Although the illustrated coil 9 is of generally rectangular construction, the present invention may advantageously be employed with round coils as well as other configurations. The belt drive with its substantial peripheral frictional engagement essentially eliminates the slippage involved in the point type contact of direct engaging drive wheel arrangements and thereby substantially increases the accuracy of tape placement.

The present invention has been found to provide a highly reliable automatic wrapping device for applying a tape in relatively precise overlapping manner to another member such as the coil.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim:

1. A winding apparatus, comprising a wrapping means continuously winding a continuous fiat strip having a sub stantially greater width than thickness about an endless member rotated relative to the wrapping means, a support plate adapted to have said member disposed thereon, adjustable mounting means connected to said support plate for positioning said plate relative to said wrapping means, an endless belt, a pair of laterally spaced drive wheels having outer friction surfaces, a plurality of guide rolls, means connected to said plate and supporting said wheels and guide rolls immediately above said plate to define a path for said belt, said belt being looped about said guide rolls and drive wheels to define a memberreceiving loop, said member being releasably disposed within said loop, means to tighten said belt to engage the outer periphery of said member and force said member outwardly and into engagement with the belt at said wheels, said wheels being spaced a distance less than the width of said member to prevent movement of the member therethrough, a shaft secured to said support and coupled to said wheels to simultaneously rotate said wheels to move said belt and thereby rotate said member past said wrapping means to produce a selected overlap of said continuous strip, a worm gear secured to said shaft, a

worm rotatably mounted and meshing with said worm gear in all positions of said plate, and means to rotate said worm.

2. The apparatus of claim 1 wherein said last named means are reversible to selectively rotate said belt in opposite directions.

3. A winding apparatus, comprising a wrapping means continuously winding a continuous flat strip having a substantially greater width than thickness about an endless member rotated relative to the wrapping means, a support plate for said endless member, an adjustable mounting means connected to said plate for positioning said plate with respect to said wrapping means, an endless belt formed of a resilient material, a pair of laterally spaced wheels having outer friction surfaces, arm means secured to said wheels and to said plate to locate the wheels to the opposite sides of the wrapping means, a plurality of guide rollers secured to said plate, said belt being looped about said guide rollers and drive wheels and being extended inwardly between said drive Wheels to define a member-receiving loop, said endless member being releasably disposed within said loop, said wheels being spaced by a distance less than the width of said member to prevent movement of the member therethrough, latch means connected to one of said guide rolls to selectively position said guide roll for tightening said belt and forcing said member outwardly and into engagement with the belt at said wheels and for releasing said belt for insertion and removal of said member, belt retainer idler rollers resiliently clamping the belt to the wheels to support the belt when changing endless members, a drive sytem connected to said plate and coupling said wheels to an input drive unit to simultaneously rotate said wheels to move said belt and thereby rotate said member past said wrapping means to produce a selected overlap of said continuous strip upon said member, said power means including a fixed power source and a coupling means connected to the input drive unit for all positions of said plate.

References Cited UNITED STATES PATENTS 2,656,124 10/1953 Stevens 242-4 2,726,817 12/ 1955 Barrows 242-4 3,050,266 8/1962 Bucalo 242-4 3,132,816 5/1964 Oshima 242-4 3 ,232,544 2/ 1966 Caldwell 242-6 FOREIGN PATENTS 1,102,256 5/1955 France 242-4 BILLY s. TAYLOR, Primary Examiner US. Cl. X.R. 

